Distributions of Particle Sizes in Black Soil and Their Environmental Significance in Northeast China

Round 1

Reviewer 1 Report

Dear Authors,

I revised the manuscript "Particle Size Characteristics of Black Soil and Their Environmental Significance, Northeast China" submitted to Sustainability journal. The manuscript is very interesting. However, I have some concerns, which need to be addressed before considering for final publication.

 

Line 136. Check the symbol before the letter "I".

 

Subsection "4.2. Spatial Differentiation of Contribution Rates of Soil Particle Size Sensitive Components" should be moved to Section 3. The content of this subsection is more suitable for the "Results" section rather than the "Discussion" section.

 

Section "5. Conclusions". Conclusions should not be a simple summary of the results. In my opinion, the focus should be on drawing conclusions from the research and identifying the reasons for the observed changes (as partially presented). Present the motivation and scope for further research on this topic.

 

Section "References". Style of the references is not in accordance with the requirements of Sustainability. I suggest using bibliography software package like Mendeley, Zotero, EndNote etc. In references 22 and 26, there are underlined parts of the text. For what purpose was this done?

Author Response

Response to Reviewer 1 Comments

Dear Assistant editor and Rewiewer of “Sustainability”

We were pleased to receive the thoughtful and helpful reviews of our manuscript titled “Particle Size Characteristics of Black Soil and Their Environmental Significance, Northeast China” with the manuscript number of sustainability-1132115, and we appreciate the opportunity to improve and resubmit our manuscript. We have revised the manuscript according to the editor and reviewers, and detail our responses below, with corresponding changes made directly to the manuscript where appropriate. Accompanying this letter, please find a revised version of our manuscript. We hope that these changes are found suitable and this manuscript can be accepted for publication in Sustainability. Thank you for your attention to our manuscript. Detailed responses to the academic editor are as follows:

 

Point 1: I revised the manuscript "Particle Size Characteristics of Black Soil and Their Environmental Significance, Northeast China" submitted to Sustainability journal. The manuscript is very interesting. However, I have some concerns, which need to be addressed before considering for final publication.

Response 1: Many thanks to the reviewer’s comments. We have revised the manuscript according to your valuable suggestions.

 

Point 2: Line 136. Check the symbol before the letter "I".

Response 2:  The formula (1) has been re-edited. We have corrected it in the manuscript. Thank you so much.

 

 

Point 3: Subsection "4.2. Spatial Differentiation of Contribution Rates of Soil Particle Size Sensitive Components" should be moved to Section 3. The content of this subsection is more suitable for the "Results" section rather than the "Discussion" section.

Response 3: Some of the contents in 4.2. have been removed to a new subsection “3.3. Spatial Distribution of Contribution Rates of Soil Particle Size Sensitive Components”. The discussion of this results remained in the “4.2. Spatial Differentiation of Contribution Rates of Soil Particle Size Sensitive Components”. The “3.3. Spatial Distribution of Contribution Rates of Soil Particle Size Sensitive Components” are as follows:

3.3. Spatial Distribution of Contribution Rates of Soil Particle Size Sensitive Components

In order to intuitively understand the topsoil spatial distribution pattern in the studied area, the Kriging method under Geostatistics tools in ArcGIS 10.2 was used to perform optimized interpolation and visualization of the spatial distribution of each of the soil particle size sensitive components (Figure 3). In Figure 3a, the contribution rate of C1 had the smallest variation within the studied area, showing no obvious spatial distribution patterns. Figure 3b points out that C2 component has the highest contribution rate in KD and BQ, and its contribution rate decreases from the center towards the eastern and western sides. The lowest C2 contribution rate appeared in the southwest corners of FY and LD. C3 component was constituted of coarse silt particles with the contribution rate ranked as: BQ < KD < FY < YA < BA < LD < KS (Figure 3c). C4 is only found across the whole FY and parts of LD and YA. C4 contribution rate is highest in FY, as high as 32.95% (Figure 3d).

 

Point 4: Section "5. Conclusions". Conclusions should not be a simple summary of the results. In my opinion, the focus should be on drawing conclusions from the research and identifying the reasons for the observed changes (as partially presented). Present the motivation and scope for further research on this topic.

Response 4: We really appreciate your helpful comments. The rewritten Conclusions was as follows:

5. Conclusions

The qualitative and quantitative degradation of Chinese northeast black soil is of great significance to food security and sustainable development. Particle size components, particle size environmental sensitive components and their indicating significances were evaluated to investigate the spatial characteristics of black soil degradation. In general, the mechanical composition of surface soil in the studied area was found to be silt (17.7%–80.3%) > clay (7.8%–79.3%) > sand (0–73.7%). Relatively high content of clay particles was found in surface black soil samples, which was significantly higher than that in Quaternary red earth, purplish soil and loess. This feature is the main reason for the higher natural nutrient capacity in black soil.

Log-normal distribution function fitting was applied to extract sensitive components that effected on the soil. Four environmental sensitive components of C1 (< 2 μm), C2 (2–15 μm), C3 (15–65 μm) and C4 (>65 μm) were identified, and their contribution rates were calculated to further reveal the impact of different factors on the black soil. C1 had the lowest contribution rate, and did not differ across locations, representing airborne dust transported from long distances away. It was caused by clay particles smaller than 20 μm can be transported across long distances in suspension form, up to thousands of kilometers. C2 had the highest contribution rate and lowest variability, representing locally developed soil from parent materials. The significantly higher contribution rate of C2 in Baiquan and Kedong than any other locations was mostly determined by the regional differentiation in the contribution rates of C3 and C4. C3 has a larger particle diameter less than 65 μm which can short-distance saltation due to the monsoon-affected wind erosion. The soil coarsening observed in the studied area mainly resulted from wind erosion effect, with minor and location-specific contributions from human activities. C4 consisted of all particles larger than 65 μm, representing effects of strong human disturbance.

Among the sampled locations, soil condition is the best in Baiquan and Kedong, with soil coarsening occurring in less than 10% of total soil. Keshan, Lindian and Fuyu are experiencing the most severe soil coarsening, with more than 40% of total soil impacted by erosion and disturbance processes. Contents of C3 and C4 were highly variable within and across locations, especially higher in Fuyu. The highest proportions of arable land in Fuyu caused the majority of soil coarsening was resulted from human activities by agricultural cultivation. Active management and regulation of human disturbance of surface soil should be implemented to protect topsoil and control soil degradation. Wind erosion contributed more to soil degradation than human activities in all other locations. As a result, soil protection acts in these areas should focus on defense against wind erosion. Planting windbreak forests should be encouraged in these areas.

 

Point 5: Section "References". Style of the references is not in accordance with the requirements of Sustainability. I suggest using bibliography software package like Mendeley, Zotero, EndNote etc. In references 22 and 26, there are underlined parts of the text. For what purpose was this done?

Response 5: Many thanks to the reviewer’s comments. The style of the references were revised according to the requirements of Sustainability. In references 22 and 26, the underlined parts were hyperlinks, which were all ready removed.

Reviewer 2 Report

Title: Particle Size Characteristics of Black Soil and Their Environ mental Significance, Northeast China

Authors: Binghe Yan et al.

Manuscript Number: sustainability-1132115

The authors studied particle size distributions in northeast China. They took samples of soils from seven counties in northeast China. While the subject is relevant and interesting, the novelty of this study is not sufficient. Furthermore, the manuscript has many shortcomings and uncertainties as it currently stands. Some comments are as the below:

1. Title is not appreciated. This was a study of distributions of particle sizes in black soil rather than Particle Size Characteristics of Black Soil. Furthermore, Comma should be replaced by in.
2. In Introduction, the authors should review particle methods of particle distribution analysis. After you introduced these methods, you need to briefly describe them one by one. How are they related to environmental factors, transportation and so on. You need to explain why you had not used them. You need to justify why you selected the present method. Why did you use the current methods? What were advantages of your approach over other approaches.
3. Ln46, particle size frequency distribution curve requires to be defined.
4. In Section 2.2, the authors took soil samples once in Aril 2015. This means the study had not included temporal factors. It is unclear how particle sizes were related to Their Environmental Significance or effects.
5. In Section 2.3, what were sensitive components? These parameters in Eq. (1) required to be defined clearly before you used them. Furthermore, you should explain these parameters why you select them.
6. Ln162-165, these ranges of compositions are too large. Therefore, what did they mean? Why did the signature represent the natural nutrient capacity in black soil? You require to explain them.
7. Ln181-183, it is well-known that soil particle size could be related to many factors, such as parent materials, source of deposit material, climate, transportation and so on. The point is that you require to reveal their relationship.
8. Ln196-203, why did BQ and KD have finer particles? You may explain what single soil source and low transportation resulted in the type of particle size after you compared with other counties.
9. Ln218-225, the sensitive components should be moved to Section 2.3. Furthermore, it is unclear that these components were to represent particle sizes or causes to make up of these sizes? How/what were they related to environmental factors?
10. In Discussion section, you should discuss limitations of this study.

Author Response

Response to Reviewer 2 Comments

Dear Assistant editor and Rewiewer of “Sustainability”

We were pleased to receive the thoughtful and helpful reviews of our manuscript titled “Particle Size Characteristics of Black Soil and Their Environmental Significance, Northeast China” with the manuscript number of sustainability-1132115, and we appreciate the opportunity to improve and resubmit our manuscript. We have revised the manuscript according to the editor and reviewers, and detail our responses below, with corresponding changes made directly to the manuscript where appropriate. Accompanying this letter, please find a revised version of our manuscript. We hope that these changes are found suitable and this manuscript can be accepted for publication in Sustainability. Thank you for your attention to our manuscript. Detailed responses to the academic editor are as follows:

 

Point: The authors studied particle size distributions in northeast China. They took samples of soils from seven counties in northeast China. While the subject is relevant and interesting, the novelty of this study is not sufficient. Furthermore, the manuscript has many shortcomings and uncertainties as it currently stands. Some comments are as the below:

Response: We really appreciate the reviewer’s valuable suggestions. We have carefully revised the whole manuscript according to your helpful comments.

 

Point 1: Title is not appreciated. This was a study of distributions of particle sizes in black soil rather than Particle Size Characteristics of Black Soil. Furthermore, Comma should be replaced by in.

Response 1: Many thanks to the reviewer’s comments. The title has been revised to “Distributions of Particle Sizes in Black Soil and Their Environmental Significance in Northeast China”.

 

Point 2: In Introduction, the authors should review particle methods of particle distribution analysis. After you introduced these methods, you need to briefly describe them one by one. How are they related to environmental factors, transportation and so on. You need to explain why you had not used them. You need to justify why you selected the present method. Why did you use the current methods? What were advantages of your approach over other approaches.

Response 2: Thanks to reviewer’s good comment. The reason we chose the method of logarithmic normal distribution function is that the other 4 methods were more suited to apply in a homogeneous environmental medium without large spatial differences, such as lake core sediments, soil profiles and ice cores. Whereas, the log-normal distribution fitting method is better suited for samples with a large spatial heterogeneity by extracting qualitative and quantitative components from polymodal curves resulting from overlapping multiple soil forming and transporting forces.

 

Point 3: Ln46, particle size frequency distribution curve requires to be defined.

Response 3: Particle size frequency distribution curve can be derived from particle size analyser, which is a smooth frequency curve with the x-coordinate are particle size diameters, and y-coordinate are the contents of each particle size diameters.

 

Point 4: In Section 2.2, the authors took soil samples once in Aril 2015. This means the study had not included temporal factors. It is unclear how particle sizes were related to Their Environmental Significance or effects.

Response 4: The surface 20 cm soil samples are robust record the materials they receive and run off in the past 1 or 2 years which can represent the environmental impact and human disturbance recently. For the current research reported in the manuscript, the environmental significances were related to the environmental impact and human disturbance which identified from particle size frequency distribution curve by logarithmic normal distribution function. Specifically speaking, the environmental significances we have reached the conclusion were long distance transported airborne deposits of clay dust (C1), successions from local parent material (C2), short distance deposits of silt particles (C3), and a component strongly disturbed by human activities (C4).

 

Point 5: In Section 2.3, what were sensitive components? These parameters in Eq. (1) required to be defined clearly before you used them. Furthermore, you should explain these parameters why you select them.

Response 5: Many thanks to the reviewer’s comments. Sensitive components can be derived from particle size frequency distribution curve, which reflect the soil formation and external influences. The Eq. (1) has been re-edited. We have corrected it in the manuscript as follows:

 

This equation is a derivation of logarithmic normal distribution function, αi and σi stand for the mean and standard deviation of the particle diameter of component i. Ci is the percentage of component i in reference to the whole sample.

 

Point 6: Ln162-165, these ranges of compositions are too large. Therefore, what did they mean? Why did the signature represent the natural nutrient capacity in black soil? You require to explain them.

Response 6: Many thanks to the reviewer’s comments. These ranges of different particle size compositions were counted from all surface soil samples. The relatively large differences were due to the spatial heterogeneity of black soil in the study area. Clay content in black soil is significantly higher than that in Quaternary red earth, purplish soil and loess. This signature particle size characteristic sets an important foundation for the higher natural nutrient capacity in black soil due to the fine particles (such as clay) have large specific surface area, which can absorb more nutrients.

 

Point 7: Ln181-183, it is well-known that soil particle size could be related to many factors, such as parent materials, source of deposit material, climate, transportation and so on. The point is that you require to reveal their relationship.

Response 7: The sensitive components derived from particle size frequency distribution curves were further investigated to reveal the relative contributions of long distance transported airborne deposits of clay dust (C1), successions from local parent material (C2), short distance deposits of silt particles (C3), and a component strongly disturbed by human activities (C4) in the black soil. In the meantime, the spatial distributions of each sensitive components were analysed, and the reasons were explained in Discussion section.

 

Point 8: Ln196-203, why did BQ and KD have finer particles? You may explain what single soil source and low transportation resulted in the type of particle size after you compared with other counties.

Response 8: Many thanks to the reviewer’s comments. Compared with other counties, BQ and KD have the relatively high forest cover rates and low arable land cover rates. Forest land has a strong function of water and soil conservation, and low arable land cover rates associated with low human disturbance, these are the reasons why BQ and KD have finer particles.

 

Point 9: Ln218-225, the sensitive components should be moved to Section 2.3. Furthermore, it is unclear that these components were to represent particle sizes or causes to make up of these sizes? How/what were they related to environmental factors?

Response 9: Many thanks to the reviewer’s comments. The contents of sensitive components (Ln218-225) were the results derived from logarithmic normal distribution function. In this case, it is not appropriate to be moved to Section 2.3. The environmental significance of the 4 sensitive components were discussed according to the characteristics of particle size diameter, soil forming processes, environmental factors, and human activities.

 

Point 10: In Discussion section, you should discuss limitations of this study.

Response 10: Many thanks to the reviewer’s comments. We have added the limitation of this study in Discussion section. The limitations were as follows:

In order to more accurately study the specific characteristics of wind erosion, such as the erosion intensity, effect factors of wind erosion, the scope of wind erosion. Control simulation tests are needed in the future, and more soil physical and chemical index (soil moisture content, soil organic carbon and pH value) are necessary.

Reviewer 3 Report

The article is focused on the particle size characteristics of black soil and their environmental significance in a selected area (northeast China). The authors present the object of research, methodological procedures and principles of statistical evaluation. The research was conducted in seven countries and cities located in the black soil area in northeast China, where 116 surface soil samples in top 20 cm were collected. In my opinion, this number of subscriptions is low. Methodical procedures for sampling and determination of composition, respective the applied statistical procedures have been defined. The results then correspond to the methodology and the authors evaluated them in a tabular and graphical manner. The results were evaluated tabular and graphically. The discussion and the conclusions partially fulfilled the character of the article. I propose to expand the article.

 

Strengths side:

- Interesting issues

- The introduction is sufficient - but I propose to add an environment

 

Weaknesses side:

- In my opinion, these are small research samples given the total area. Sometimes it happens that on an area of ​​up to 100 ha there are two to three types of soil.

- The title mentions the environmental significance - the article devotes a small space to the area

Other comments:

185 - the values ​​described in the text do not match the values ​​in the table

Author Response

Response to Reviewer 3 Comments

Dear Assistant editor and Rewiewer of “Sustainability”

We were pleased to receive the thoughtful and helpful reviews of our manuscript titled “Particle Size Characteristics of Black Soil and Their Environmental Significance, Northeast China” with the manuscript number of sustainability-1132115, and we appreciate the opportunity to improve and resubmit our manuscript. We have revised the manuscript according to the editor and reviewers, and detail our responses below, with corresponding changes made directly to the manuscript where appropriate. Accompanying this letter, please find a revised version of our manuscript. We hope that these changes are found suitable and this manuscript can be accepted for publication in Sustainability. Thank you for your attention to our manuscript. Detailed responses to the academic editor are as follows:

 

Point 1: The article is focused on the particle size characteristics of black soil and their environmental significance in a selected area (northeast China). The authors present the object of research, methodological procedures and principles of statistical evaluation. The research was conducted in seven countries and cities located in the black soil area in northeast China, where 116 surface soil samples in top 20 cm were collected. In my opinion, this number of subscriptions is low. Methodical procedures for sampling and determination of composition, respective the applied statistical procedures have been defined. The results then correspond to the methodology and the authors evaluated them in a tabular and graphical manner. The results were evaluated tabular and graphically. The discussion and the conclusions partially fulfilled the character of the article. I propose to expand the article.

Response 1: We really appreciate the reviewer’s valuable suggestions. We have carefully revised the whole manuscript according to your helpful comments.

 

Point 2: Strengths side:

- Interesting issues

- The introduction is sufficient - but I propose to add an environment

Response 2: Thank you very much for your approval of this study.

 

Point 3: In my opinion, these are small research samples given the total area. Sometimes it happens that on an area of up to 100 ha there are two to three types of soil.

Response 3: Many thanks to your helpful comment. We will increase the number and density of soil samples to make the research more meaningful.

 

Point 4: The title mentions the environmental significance - the article devotes a small space to the area.

Response 4: We really appreciate the reviewer’s valuable suggestions. The title has been revised to “Distributions of Particle Sizes in Black Soil and Their Environmental Significance in Northeast China”. The environmental significance here refers to the indicating significances of different particle size components in the black soil. For example, the environmental significances we have reached the conclusion were long distance transported airborne deposits of clay dust (C1), successions from local parent material (C2), short distance deposits of silt particles (C3), and a component strongly disturbed by human activities (C4).

 

Point 5: 185 - the values described in the text do not match the values in the table.

Response 5: Thanks very much for your suggestion. We have carefully check the data, and we found that the values described in the text and in the table are consistent. We guess you may have query about the medium diameter of the whole samples which ranged from 1.71 to 142.67 μm and the mean value of medium diameter which is 13.07 μm. The large medium diameter of 142.67 μm was found in Fuyu.

Round 2

Reviewer 2 Report

The authors have improved. I recommend it to be accepted.

Author Response

Response to Reviewer 2 Comments

Dear Assistant editor and Reviewer of “Sustainability”

Thank you very much for your valuable suggestions for our manuscript. We appreciate all your hard word!

Point: The authors have improved. I recommend it to be accepted.

Response: We really appreciate the reviewer’s valuable suggestions. 

Reviewer 3 Report

1. The authors did not fully meet my requirements. From the point of view of the article, it was not expanded in such detail.
2. I suggest adding the information I requested.

- Add a more detailed description - environmental significance directly to the article not only in the answer for me.

How many samples did you extend the research sample

Author Response

Response to Reviewer 3 Comments Dear Assistant editor and Reviewer of “Sustainability” We feel so sorry that we did not understand the reviewer’s comments very well, and caused the manuscript did not fully meet the reviewer’s requirements. We are very sorry for waste your time. We have carefully revised the manuscript, and the corresponding details are added to the manuscript according to the reviewer’s comments. We hope that these changes are found suitable and this manuscript can be accepted for publication in Sustainability. Thank you for your valuable suggestions to our manuscript. Detailed responses about Round 1 and Round 2 are as follows: Review Report (Round 2) Point 1: The authors did not fully meet my requirements. From the point of view of the article, it was not expanded in such detail. Response 1: Thanks for the reviewer giving us one more chance to revise and improve the manuscript. More details about the environmental significance have been expanded in the manuscript. They are as follows: 1. Introduction Section: The background and significance of the research have been added to introduce the environmental problems of the black soil. “Although the time of land reclamation in the black soil area is relatively short, the area of accelerated erosion after reclamation is very wide. The black soil layer has decreased from 70~100 cm in the early reclamation period to 16–70 cm in the 1980s, and the or-ganic matter contents has decreased from 6%–15% to 1.98%. Soil erosion reduced the thickness of effective soil layer, deteriorates the physical and chemical properties of soil, and leads to the decrease of land productivity.” 2. 3.1. Soil Particle Size Characteristics Section: The reason of the differences of soil mechanical composition among the regions from the land cover aspect have been added. “Compared with other counties, BQ and KD have the relatively high forest cover rates and low arable land cover rates. Forest land has a strong function of water and soil conservation, and low arable land cover rates associated with low human disturbance, these are the reasons why BQ and KD have finer particles.” 3. 4.1. Environmental Implications of Soil Particle Size Sensitive Components Section: Discussions about the soil particle size sensitive components have been added to interpret the environmental significance. “The results were in accord with that the fine silt was the dominant soil mechanical composition of black soil.” “It is reported that soil erosion area in the black soil region in northeast China was 74326.2 km2, while the wind erosion area was about 22448.2 km2, accounting for 30.2% of the total erosion area [36]. Spring and autumn seasons in the studied area are characterized by heavy wind and high evaporation rate due to the surface soil was dry and loose, resulting in low surface soil water content. Furthermore, black soil region was located in the seasonal frozen soil area, the freeze-thaw cycle could decrease bulk density, loose structure and weaken corrosion resistance of soil, which created favorable conditions for wind erosion. If exposed land areas, such as agricultural lands, are not protected by windbreak forests, coarse silt particles are extremely susceptible to short-distance low-altitude wind transportation, resulting in increased contribution rate of wind-erosion component (C3).” “One of most serious problems in the northeast China is that the overuse and low maintenance, weak awareness of black soil protection, which have caused the deterio-ration of physical properties, decreased of water stable soil aggregate structure, and declined cohesion among the soil particles.” “The proportions of arable land of 7 regions in 2014 were counted to evaluate the degree of anthropogenic disturbance to topsoil, which ranked as: BQ (69.9%) < KD (78.7%) < YA (88.5%) < BA (92.1%) < KS (94.0%) < LD (95.7%) < FY (96.5%) in Figure 4. The highest proportions of arable land in FY indicated that the majority of soil coarsening was resulted from human activities by agricultural cultivation.” “In windy weather, wind erosion was easily occurred in the surface soil of arable land with more human disturbance.” Point 2: I suggest adding the information I requested. Response 2: The information was added according to the reviewer’s suggestion. We hope the revision meet the reviewer’s requirements. Point 3: Add a more detailed description - environmental significance directly to the article not only in the answer for me. Response 3: We really appreciated the reviewer’s helpful comments. More detailed description about the environmental significance have been added in the manuscript as the contents in Response 1. Thank you very much. Point 4: How many samples did you extend the research sample Response 4: We have collected 126 surface soil samples in the current research. The detail are as follows: according to the even distribution sample principle, we determined 6 sampling locations per county/city, each separated by one 1 m x 1 m unit, resulting a total of 42 sampling locations. Three soil samples were taken from each sampling location using the diagonal sample method. However, there were 10 samples belong to outlier samples, and finally 116 samples were analysed.

Author Response File: Author Response.pdf